In a bipolar battery in which a plurality of bipolar electrodes, each having a positive electrode active material layer formed on one surface of a collector and a negative electrode active material layer formed on another surface of the collector, are laminated via an electrolyte layer. Unit cells constituting such a bipolar battery may have a fluctuation in its performance such as an internal resistance, capacity, and so on due to factors arising during manufacture. The unit cells are connected in series for use in the bipolar battery. However, when variation exists in a voltage of each unit cell, deterioration advances from a unit cell having a high voltage, and as a result, a life of the entire bipolar battery shortens.
To extend the life of the entire bipolar battery, therefore, the voltage of each unit cell is preferably measured, whereupon the voltage of each unit cell is adjusted on the basis of the measured voltages.
JP 2005-235428A, published by the Japan Patent Office in 2005, teaches that in order to measure the voltage of each unit cell of a bipolar battery, a voltage detection terminal is to be attached to the collector of each unit cell so that a voltage can be extracted from each unit cell and measured.